The Source for Java Developers.
http://java.sun.com/

Code Samples and Apps (SDN.)
http://java.sun.com/developer/codesamples/

Java Examples from The Java Developers Almanac 1.4.
http://javaalmanac.com/

Java examples (example source code) Organized by topic.
http://www.java2s.com/

KickJava.com: Java API By Example, From Geeks To Geeks.
http://www.kickjava.com/

Java Examples in Open Source Code.
http://www.jexamples.com/

Servlets.com.
http://servlets.com/

Sun Java, JSP and J2EE technology programming forums and tutorials.
http://www.javalobby.org/